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Cofrin Center for Biodiversity

•  THE VECTOR DATA MODEL  •

There are millions of spatial databases in the geospatial technology universe. Most employ the raster data model for storing and georeferencing data. The vector data model accounts for virtually all of the remainder. It's based on using simple geometric shapes to describe the locations of objects and conditions on the earth's surface. There's lots of explanatory material out there. Here are some articles that we've found helpful:

Vector data is stored in data structures called "feature classes" which come in three flavors - point, line and polygon.

Point Feature Classes
A point feature class is used to store spatial and tabular information for a group of objects or conditions on the earth's surface whose locations can be expressed in terms of discrete points. City centers, crime sites, critter sightings, etc. are just a few examples.
The spatial information for each feature is mapped in one of two ways. A single-part point feature is mapped using one coordinate pair. A multi-part point feature is mapped using one coordinate pair for each of its several points.
Whether the feature is single-part or multi-part, its descriptive information is located in a single data row in the feature class attribute table.

Line Feature Classes
A line feature class is used to store spatial and tabular information for a group of objects or conditions on the earth's surface whose locations can be expressed in terms of open geometric figures. Watercourses, street centerlines, tornado tracks, etc. are just a few examples.
The spatial information for each feature is mapped in one of two ways. A single-part line feature is mapped using one chain of coordinate pairs. A multi-part line feature is mapped using one chain of coordinate pairs for each of its several lines.
Whether the feature is single-part or multi-part, its descriptive information is located in a single data row in the feature class attribute table.

EXAMPLE - Our geospatial data archive contains a "Brown County Street Centerlines" database. Each of the 26,000 records in the database includes a list of the coordinate pairs that define the location of one street segment. Each record also includes a set of 50 attribute values pertaining to that segment - Name1, Name2, Type, SPEED_LIMIT to list a few. This database does not include any multi-part features. Think about why that makes perfect sense.

Polygon Feature Classes
A polygon feature class is used to store spatial and tabular information for a group of objects or conditions on the earth's surface whose locations can be expressed in terms of closed geometric figures. Water bodies, land parcels, administrative boundaries, etc. are just a few examples.
The spatial information for each feature is mapped in one of two ways. A single-part polygon feature is mapped using one chain of coordinate pairs with the ends of the chain joined to form a closed figure. A multi-part polygon feature is mapped using one chain of coordinate pairs for each of its several closed figures.
Whether the feature is single-part or multi-part, its descriptive information is located in a single data row in the feature class attribute table.